Comparison of the Performance of Grid-Forming Converters with Different Combinations of Control Methods and Current Limiters

As fossil fuel-based synchronous generation is rapidly phased out and replaced with inverter-based renewable energy sources with grid-following (GFL) converter controls, system strength and grid stability will weaken dramatically. To address this issue, grid-forming (GFM) controls have been developed with a focus on voltage and frequency support, inertia provision, and oscillation damping. Many GFM control methods have been proposed in the literature, such as droop control, virtual synchronous generator (VSG), and virtual oscillator control (VOC). An important consideration for inverter-based resources (IBRs) is the limited overcurrent capability of the semiconductor switches. Thus, current limiting control is crucial for the design of GFM converters, and many different methods have been proposed. This paper compares the performance of three GFM control methods under the impact of three current limiting methods, considering fault response and synchronization stability. Practical insights are drawn from simulation results and verified through hardware experiments. It is found that droop control exhibits the lowest transient voltage overshoots regardless of which current limiting method is used, the inertia response of VSG control is greatly diminished by conservative current limits, and VOC may exhibit synchronization instability when paired with the circular current limiter or virtual impedance.